Battery charging apparatus



June 9, 1942. R. E. SEARS BATTERY CHARGING APPARATUS 2 Sheets-Sheet 1Filed Aug. 2, 1940 0a m 5 5 z z ,0 7 a Q @Vfi J Z 4 2 \z 2 M INVENTOR.flaw/ma ET 567??5 June 9, 1942. R. E. SEARS BATTERY CHARGING APPARATUSFiled Aug. 2, 1940 2 Sheets-Sheet 2 it x: m a v ma w m M 3 m n Z W w m lw 2 T M INVENTOR. EICHHRD E. SEA/e5 ATTORNEYS Patented June 9, 19422,285,620 BATTERY CEAIGING APPARATUS Richard 15. Sears, Cleveland, Ohio,

Willard Storage Battery Ohio, a corporation of West asaignor to Company,Cleveland.

Virginia Application August 2, 1940, Serial No. 349,937

scrum.

. This invention relates to the charging of storage batteries, and moreparticularly to improved charging apparatus with which it is possible tomaterially shorten the charging period without subjecting the battery toinjurious effects.

In the charging of storage batteriesas ordinarily carried out, arelatively low charging rate has been employed and a period of severalhours has been required to restore the battery from a dischargedcondition to a charged condition. To shorten the charging period it hasbeen proposed to employ charging apparatus providing a relatively highcharging rate or current for a relatively, shorter period of time. sucha relatively high charging rate or current has certain disadvantages,one of which is that a relatively rapid increase in battery temperaturemay occur and the temperature may reach a value suiliciently high tocause weakening of the separators and to produce other injuriouseffects. Another disadvantage is that the high charging rate is likelyto be accompanied by excessive gassing which is not only wasteful oicurrent but tends to cause particles of the active material to becomeloosened or separated from the plates. Moreover, the condition of theordinary discharged battery is such that a relatively high chargingcurrent can be satisfactorily used during the early. part of thecharging period, but if maintained throughout the entire chargingperiod, it will produce excessive gassing, overheating and otherunsatisfactory or harmful conditions.

By my invention these disadvantages are overcome and an improved highrate charging apparatus is provided with which the battery temperaturecan be kept below an injurious point and the portion of current whichcauses gassing can be kept at a relatively low or nominal value. As willbe explained hereinafter, I make use of changes in the terminal voltageof the battery to so control the charging circuit as to preventexcessive gassing or an injurious increase in battery temperature.

It is, therefore, an object of this invention to provide improvedbattery charging apparatus in which means responsive to changes in theterminal voltage of the battery being charged operates to control thecharging circuit so that a relatively high rate of charge can bemaintained without causing overheating of the battery or excessivegassing.

Another object of my invention is to provide improved battery chargingapparatus in which means responsive to a predetermined change in The useof a condition of the battery causes a step-by-step decrease in thecharging current or rate.

Still another object of my invention is to provide improved batterycharging apparatus of the type referred to having a relay arranged to beconnected across the terminals of the battery to be charged and a magnetcontrolled by the contacts of the relay and operable to cause astep-by-step decrease in the charging curren or rate.

It is also an object of my invention to provide improved batterycharging apparatus 01' this character in which a time delay device and acompensating means are provided for adjusting the operation of the relayto compensate for variations in the temperature or other conditionof thebattery to be charged.

Other objects and advantages of my invention will be apparent from thefollowing description when taken in conjunction with the accompanyingsheets of drawings, in which,

Fig. 1 is a diagrammatic view showing a battery charging system orapparatus embodying my invention;

Fig. 2 is another view, more or less diagrammatic in form, showingportions of the same system and further illustrating the constructionand operation of the means for varying the charging rate or current; and

Fig. 3 is a diagram or graphic illustration of the functioning of myimproved charging apparatus.

Further reference will now be made to the accompanying drawings for thepurpose of describing my improved charging apparatus and the operationthereof more in detail, but it will be understood, of course, that theparticular apparatus herein illustrated and described in detailrepresents but one embodiment and that the invention may be applied tovarious other forms and arrangements of apparatus of this type.

In the present embodiment of my charging apparatus, as illustrated inFig. l, I provide a charging circuit having relatively heavy leads orconductors i and I adapted for connection with the terminals of astorage battery B to be charged, and a control means which is responsiveto predetermined changes in the terminal voltage of the battery andaiiects the charging circuit 30 as to correspondingly vary the chargingcurrent or rate. The source of current for' charging the battery B maybe a pair of alternating current line conductors l0 and H and atransformer I! having a primary winding l3 connected with such lineconductors by the switch M. A suitable fuse IE, or the like, may beincluded in the primary circuit of the transformer. The charging circuitmay include the secondary winding IQ of the transformer 12 and arectifier II which may be of any appropriate construction, but is hereshown as being of the dry disk bridge type. An ammeter l8 may alsobe'included in the charging circuit.

For varying the charging current and the rate of charge of the batteryB, I provide a tap switch 28 in the charging circuit having a pluralityof spaced contacts 2| connected with different portions Or sections ofthe transformer secondary It by taps 22. The switch 29 also has amovable contact or arm 23 which can be shifted to different positions orsettings for reducing the charging current or rate as the charging opration progresses. The spacing of the contacts 2| of this switch arepreferably such that the movable contact or arm 23 must completelydisengage one contact and open the.charging circuit before it moves intoengagement with the next adjacent contact. In other words, the spacingof the contacts is such that the arm: 23 must move through anintermediate position represented by the line or mark 24 while travelingfrom one contact to thenext adjacent one. In the switch 29, as hereshown, the contact 2|a represents the position or setting of the arm 23.for the smallest charging current or lowest charging rate and thecontact 2|b represents the position or setting of the arm 23 for themaximum charging current and the highest charging rate. The line or mark25 lying beyond the extreme contact 2|a represents the ultimate or finalposition of the movable arm 23.

I find it desirable to actuate the switch 29 with a step-by-stepmovement and to thisend I may provide means which constantly biases orurges the movable contact arm 23 toward its final position 25; that is,in a direction to decrease the charging rate, and an escapement forlimiting the movement of the contact arm by the biasing means. A deviceof this kind is shown in Fig. 2 as comprising an escapement member 21which is rotatable or oscillatable on a stationary shaft or pin 28 andcarries the contact arm 23 which is moved thereby to engage the contacts2| in the manner above explained. The escapement member 21 may be in theform of a casing or wheel having a series of peripheral teeth 29 forcooperation with an escapement lever 39.

A spiral spring 3| may be'employed as the biasing means which urges themember 21 in a direction to cause the contact arm 23 to be moved towardits final position 28. This spring may have one end thereof anchored tothe shaft 29,

as indicated at 32, and may have its opposite end.

suitably connected with the member 21 as by means of thepin 33. Theescapement lever 39 may have arms 39a and 39b which retard thecounterclockwise movement of the member 21 under the influence of thespiral spring 3| and may be mounted for rocking movement on the pin 39to alternately bring such arms into the path of the movement of theteeth 29. A tension spring 36 may be connected with a projecting portion300 of the escapement lever 39 so as to overbalance this lever andnormally hold the same in a setting with the arm 39a thereof in aposition to be engaged by one of the teeth 29.

Fig. 2 shows the escapement lever 39 with the arm 39a thereof engaged bythe tooth 29a and also shows the contact arm 23 in engagement tion bythe escapement lever. when the lever '30 is rocked from this position,the arm 39a thereof will disengage the tooth 29a permitting the spiralspring 3| to rotate the member 21 in a counter-clockwise direction. Thissame rocking of the lever 39 will bring the arm 39b thereof into thepath of the tooth 29b and the counterclockwise rotation of the member 21will be stopped thereby with the contact arm 23 occupying a positionintermediate two adjacent contacts 2| as represented by the line 24. Thereturn of the escapement lever 39 to the position shown in Fig. 2 underthe influence of the spring 36 will disengage the arm 39b from the tooth29b and will again bring the arm 39a into a position to be engaged by asucceeding tooth, and timedditional counterclockwise movement thuspermitted the member 21, shifts the contact arm 23 from the intermediateposition 24 to the next succeeding contact. The cooperation of the lever39 with the teeth 29 thus permits a stepby-step movement of the contactarm 23 by the spiral spring 2|.

with one of the contacts 2| and held in this posi- For controlling theabove-described operation of the tap switch 23 in response to apredetermined change in the condition of the battery B being charged-Imay provide a solenoid 38 for rocking the escapement lever 30 inopposition to the spring 36 and a relay 39 for controlling theenergization of the solenoid. This relay may be of any suitableconstruction, and as here shown, has an energizing winding or coil 49and a movable armature 4| for opening and closing the contacts 42 and43. The relay winding 40 may have opposite ends thereof connected withthe terminals of the battery B so as to be responsive to changes in thevoltage thereof. A tension spring 44 acts on the armature 4| to normallyseparate the contacts 42 and 43.

The solenoid 38 is arranged adjacent the portion 390 of the escapementarm 39 so that upon energization of the solenoid this arm will be rockedon the pivot 35 in a counterclockwise direction for the purpose aboveexplained, and when the solenoid is deenergized the arm will be rockedin a clockwise direction by the spring 36. The winding of the solenoid38 is arranged to be energized from the line connections from which theprimary l3 of the transformer I2 is energized but such energization ofthe solenoid winding is controlled by the contacts 42 and 43 of therelay. I may also provide a manually operable push button switch 45, orthe like, in a shunt around the relay contacts 42 and 43 so that thesolenoid 38 can be energized by a manual closing of this switchindependent of the relay 39.

In the operation of the apparatus above describedgthe leads 8 and 9 ofthe charging circuit are connected to the terminals of the battery B tobe charged. The switch I4 is closed to energize the transformer I2. Atthis time the switch arm 23 is in the position represented by the mark25 and the charging circuit is then open. It is desirable to start thecharging of the battery with the highest available charging current orrate and, therefore, the arm 23 is swung into engagement with thecontact 2|b. This swinging of the arm 23 rotates the toothed member orescapement wheel 21 in a clockwise direction causing the spiral spring30 to be wound or stressed so as to produce a bias or tendency to swingthe arm 23 toward its released position 25.

At the beginning of the charging operation the terminal voltage of thebattery B will be relaa as be t r flv el o the n o a val e w i h to beclosed and the aaabcve tep-brat actuation of the t a 01 the battery tobe charged isgnlthatlutvit would be desirable to operation at themaximum charging rate for a given period of time without causingoperation or the relay It. This situation may occur when the temperatureof the battery is relatively low at the start or. the chargingoperation. However, when a cold batteryischargedthereisasuddenriseintheterminal voltage aiter which the value becomesredueed'to a more normal point. It the relay were permitted torespondtothlssuddenrisein terminal voltage it would be immediately trippedwithout any need for reducing the charging rate. To prevent suchpremature'operation o! the relay I may provide a time delay device 41 incircuit with the relay winding 40.compriseareaistancellintherelaycircuit and an automatically operatingswitch ior short-circuiting this resistance out 0! the relay circuit.The switch ll may be actuated by a suitable time device II which can beset or ad- Justedtocauseclosingoitheswitchllaiterthelapseoiacertainintervaloitime. Thusii the battery to be charged is ina relatively cool condition, the maximum charging rate can be saielymaintained during the first part of the charging operation and the timedevice II can, therefore, be set for a corresponding interval of timeduring which the resistance 40 will remain in the relay circuit and ahigher voltage will be needed to operate the relay. After the lapse 0!this time interval the switch II will be closed to short-circuit theresistance 48 and thereafter the relay II will be responsive to theterminal voltage 0! the battery and will exercise the control i'unctionabove explained.

5cm operation continues at ing or adiusting the eflectiveness oi therelay Iiandthismaycompriseavariable resistance 52 which is also locatedin the circuit oi. the relaywindingll. whenthe t npcraiaueoithe batte yto bechargedls initiallylowatthestart or the charging operatim, anincreased portion oftheresistancellcanbeplacedintherelay circuit so thata higher voltage will be needed totrlptherelayandhencethehigherchargingrate will be maintained. By placing more or less of the resistance II inthe relay circuit, the operaitng characteristics 0! the relay can bethus adjusted to correspond more or less with the con dition of thebattery to be charged. The resistance 52 can be adjusted to the desiredsetting at the start of the charging operation and also, if desired,from time to time as the charging progreases. Difierent points on theresistance 52 can be calibrated in terms of the operating or closingvoltage for the relay It.

I have explained above that a manually operable switch ll may beincluded in the circuit of the winding of the solenoid 38. The purposeof this switch is to enable the operator to manually reduce the chargingrate or return the switch arm 23 to its final position 25 ii conditionsshould make this desirable. The switch 45 is normally open, but can becloud or repeatedly closed by the operator to cause successivestep-by-step movements oi the switch arm 23 toward its final position25. This manual actuation of the switch It may be necessary or desirablewhen it is observed that the battery being charged is not properlytaking the charge as may be indicated by excenive gassing. It mayalsooccurthatahighiysulphatedbatteryisconnectedinthechargingcircuitandmaybegintogasviolentlyattertheflrstfewminutes of harsing without the occurrenceof a sumcient increase in the terminal voltage to actuate the relay ll.Under these circumstances the operatorwouldshiittheswitcharmntoareducedcharging rate by actuation oi the switch ll.

The toregoing explanation oi. the operation of my improved chargingapparatus can, perhaps, be better understood it reference is made toFig. 3 which graphically illustrates the functioning of my apparatus. Inthis view the curve It shows the temperature increase which occurs in abattery being charged. Thecurve II representsthe terminal voltage of thebattery during the chargingoperationandtheirregularltles liinthis curverepresent the changes which occur in the terminal voltageastheresultottheiunctioning oitherelayflandthedecreasingotthecharging currentcaused by the step-by-step movementsottheswitcharmll. Inthemnctioning oithe apparatus represented by the particularcurveshereshowmtherelaywassetbymeans oi'thevariableresistaneelltocloseoroperate at approximately 7.6 volts and this explains why theterminal voltage drops a ruptly whenever thecurveapproachesthisvalue.Thecurve" shows how the charging current is decreased progressively asthe result of the operation of the relay to progressively reduce thecharging rate. The curve 58 represents the gassing currentanditwillbeseenfromthisgraphioillustrationthatthevalueotthegassingcurrentiskept at a relatively low value during the operationoimychargingapparatus.

Promtheioregoing descrlptlonand theaccompanyingdrawingsitwillnowbereadilyseenthat Additional means may beprovided for alter- I have provided improved charging apparatus byproduced in the charging rate in response to predetermined increases inthe terminal voltage of the battery being charged. Likewise, it will beseen that I have provided my improved charging system with means foradjusting the same to compensate for variations in the condition of thebatteries to be charged. I

While I have illustrated and described my improved charging apparatus ina more or less detailed manner, it will be understood, of course, that Ido not wish to be limited to the particular arrangements and details ofconstruction herein disclosed, but regard my invention as including suchchanges and modifications as do not constitute a departure from thespirit of the invention and the scope of the appended claims.

Having thus described my invention, I claim:

1. In a battery charging system, a transformer having a plurality oftaps, a rectifier, a chargins circuit adapted for connection with abattery to be charged and including said rectifier and a switch membercooperating with said taps, means biasing said switch member in a givendirection, a toothed member and cooperating escapement lever forlimiting actuation of said switch member by said biasing means, a relayhaving circuit connections for connecting the same across the terminals.01 the battery being charged and also having contacts adapted to beclosed in response to a predetermined increase in the terminal voltageof the battery, a solenoid controlled by the contacts oi the relay andarranged to actuate said escapernent lever, and means for delayingtheoperation of the relay during the start or the'ableresistanceinthereleycircuittorediustins' cersinscoerationmpsisinssreslstsnccinthe relay circniasswitdrarranged toshort-circuit saldresktlficemdatimkildevicemmbcloseseidswitchflmthclsyseoianndeter- 21A chersins system comprising a"charm sdspted to: connection with the terminalsofabettery tobe chargedendhaving means movable to decrease the charging rate, means for causingactuation of said movable means"- inciudim a mm, a relay having eontsctscontrolling said magnet, circuit connections torthereisyconnectingthesame ecrosstbe terminals oi the battery, and means forpreventing operation of the relayduring the stertot the charm of a coldbattery comprising a resistmeans for causing sctuationqor said movable.

means a magnet, a relay havins contacts controlling said magnet, circuitconnec- 'tionsfor the relay connecting the same across the terminalsoibattery, means for delaying the operation or the relay during the startoi the operation comprising, a resistance in the;- relay circuit, aswitch arranged to shortcircuit resistance ands timing device adeptedsaidswitcbuponthelepee otapredetermined time interval, and a manuallyvarithe operating characteristics of the relay in accordance withtemperature of the battery at the start of the cm operation RICHARD E.BEARS.

